Locative abc_f_ refers to abc
in locale f;indirect locative abc__xy
refers to abc in the locale whose name is the current value
of xy. For compatibility with previous versions,
the non-standard abc__ is accepted and is the same
as abc_base_.Thus:

A name is global if it is not assigned by =.
within Explicit Definition (:).
Every global name is executed in the current locale.
Initially, the current locale is base.
A locative f_abc_,while it is executing,
switches the current locale to abc.
The verb18!:4
also switches the current locale,
and18!:5gives its name.

The name f_abc_ is executed in locale abc
in the sense that a global name referenced in f
is sought therein and, if not found, is then sought in the
locales in the path of abc
(but is still executed in abc).
The path of a locale is initially ,<,'z' ,
except that locale z has an empty path initially,
and may be changed using18!:2 .

A locale is commonly populated by a script, by appropriate
naming of the verb used to execute the script.
For example, if the file stats contains the script:

The example also illustrates the use of locale paths,
in this case the z locale: First,
the utility ssx is defined in the z locale.
In executing ssx_a_, ssx is not found in
locale a and is therefore sought (and found) in
locale z.Since ssx_a_ is executed
in locale a,the names in the stats script are
defined in locale a,populating it thereby.
Similarly for ssx_bc_.

See also18!:in
Appendix A and the “Locales” and “Object Oriented Programming”
labs distributed with the system.